Integrated circuit

ABSTRACT

A wireless communication base station device which makes it possible to provide a base station, terminal and CCE allocation method capable of reducing the number of times blind decoding of a terminal is performed, without increasing the CCE block rate, even when a plurality of unit bands are set in a terminal. In this device, a search space setting section (103) sets in each of a plurality of unit bands a common search space in respect of a terminal which is communicating using the plurality of unit bands and other terminals, and sets in each of the plurality of unit bands an individual search space in respect of the terminal. An allocation section (106) allocates control information solely to CCEs within the common search spaces set in specified unit bands among the plurality of unit bands, or solely to CCEs within individual search spaces set in specified unit bands.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation of U.S. patent application Ser. No. 16/856,368filed on Apr. 23, 2020, which is a continuation of U.S. patentapplication Ser. No. 16/245,944 filed on Jan. 11, 2019, which is acontinuation of U.S. patent application Ser. No. 15/634,376 filed onJun. 27, 2017, entitled INTEGRATED CIRCUIT″, which is a continuation ofU.S. patent application Ser. No. 15/098,623 filed on Apr. 14, 2016,entitled “TERMINAL APPARATUS AND COMMUNICATION METHOD” which is acontinuation of U.S. patent application Ser. No. 13/388,473, filed onFeb. 2, 2012, entitled “WIRELESS COMMUNICATION BASE STATION DEVICE,WIRELESS COMMUNICATION TERMINAL DEVICE, CCE ALLOCATION METHOD AND CCEBLIND DECODING METHOD”, which is the National Stage Entry ofPCT/JP2010/005070, filed on Aug. 16, 2010, which claims benefit ofJapanese Patent Application No. 2009-188721 filed on Aug. 17, 2009, theentireties of which are incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to a radio communication base stationapparatus, radio communication terminal apparatus, CCE assignment methodand CCE blind decoding method.

BACKGROUND ART

In 3GPP-LTE (3rd Generation Partnership Project Radio Access Long TermEvolution, hereinafter referred to as “LTE”), OFDMA (OrthogonalFrequency Division Multiple Access) is used as a downlink communicationmethod, and SC-FDMA (Single Carrier Frequency Division Multiple Access)is used as an uplink communication method (see Non-Patent Literatures 1,2, and 3, for example).

In LTE, a radio communication base station apparatus (hereinafterabbreviated to “base station”) performs communication by assigningresource blocks (RB) within a system band to a radio communicationterminal apparatus (hereinafter abbreviated to “terminal”) in time unitscalled “subframes.” Also, a base station transmits assignment controlinformation (L1/L2 control information) for notifying downlink data anduplink data resource assignment results to a terminal. This assignmentcontrol information is transmitted to a terminal using a downlinkcontrol channel such as a PDCCH (Physical Downlink Control Channel), forexample. Here, each PDCCH occupies a resource comprising one or acontinuous plurality of CCEs (Control Channel Elements). In LTE, anumber of CCEs occupied by a PDCCH (linked number of CCEs: CCEaggregation level) is selected as one of 1, 2, 4, or 8, according to thenumber of information bits of assignment control information or thechannel state of a terminal. In LTE, a frequency band having a maximumwidth of 20 MHz is supported as a system bandwidth.

Also, a base station transmits a plurality of PDCCHs simultaneously inorder to assign a plurality of terminals to one subframe. At this time,the base station transmits a CRC bit masked (or scrambled) by atransmission-destination terminal ID, included in a PDCCH, in order toidentify a transmission-destination terminal of each PDCCH. Then aterminal performs blind decoding of a PDCCH by demasking (ordescrambling) a CRC bit with that terminal's terminal ID in a pluralityof PDCCHs for which there is a possibility of that terminal beingaddressed.

Furthermore, assignment control information transmitted from the basestation is called “DCI (Downlink Control Information)” and includesinformation on resources assigned by the base station to the terminal(resource assignment information) and MCS (Modulation and channel CodingScheme) or the like. The DCI has a plurality of formats for uplink, fordownlink MIMO (Multiple Input Multiple Output) transmission and fordownlink non-continuous band assignment or the like. The terminal needsto receive both downlink assignment control information(downlink-related assignment control information) and uplink assignmentcontrol information (uplink-related assignment control information)having a plurality of formats.

For example, the downlink assignment control information defines formatsin a plurality of sizes according to a transmitting antenna controlmethod and resource assignment method or the like of the base station.Of the plurality of formats, a downlink assignment control informationformat for performing continuous band assignment (hereinafter simplyreferred to as “downlink assignment control information”) and an uplinkassignment control information format for performing continuous bandassignment (hereinafter simply referred to as “uplink assignment controlinformation”) have the same size. These formats (DCI formats) includetype information (e.g., 1-bit flag) indicating the type of assignmentcontrol information (downlink assignment control information or uplinkassignment control information). Thus, even when the DCI size indicatingthe downlink assignment control information and the DCI size indicatingthe uplink assignment control information are the same, the terminal canidentify whether the assignment control information is the downlinkassignment control information or uplink assignment control informationby checking the type information included in the assignment controlinformation.

The DCI format used when uplink assignment control information forperforming continuous band assignment is transmitted is called “DCIformat 0” (hereinafter referred to as “DCI 0”) and the DCI format usedwhen downlink assignment control information for performing continuousband assignment is transmitted is called “DCI format 1A” (hereinafterreferred to as “DCI 1A”). As described above, DCI 0 and DCI 1A have thesame size and can be distinguished by type information, and thereforeDCI 0 and DCI 1A will be represented collectively as “DCI 0/1A.”

In addition to the above-described DCI formats, there are DCI format 1(hereinafter referred to as “DCI 1”) for performing non-continuous bandassignment on a downlink and DCI formats 2 and 2A (hereinafter referredto as “DCI 2 and 2A” for assigning spatial multiplexing MIMOtransmission. Here, DCI 1, 2 and 2A are formats used in dependence onthe downlink transmission mode of the terminal (non-continuous bandassignment or spatial multiplexing MIMO transmission) and are formatsset for each terminal. On the other hand, DCI 0/1A is a formatindependent of the transmission mode, format that can be used for aterminal in any transmission mode, that is, format that can be usedcommonly for all terminals. Furthermore, when DCI 0/1A is used, 1antenna transmission or transmission diversity is used as a defaulttransmission mode.

Furthermore, a method has been investigated that limits CCEs subject toblind decoding for each terminal in order to decrease the number ofblind decoding operations to reduce the circuit scale of a terminal.With this method, a CCE area (hereinafter referred to as “search space”)that is subject to blind decoding is limited for each terminal. In LTE,a search space is set randomly for each terminal, and a number of CCEsincluded within a search space is defined for each PDCCH CCE aggregationlevel. For example, for CCE aggregation levels 1, 2, 4, and 8,respectively, the number of CCEs included within a search space, thatis, the number of CCEs subject to blind decoding, is limited to sixcandidates (6(=1×6) CCEs), six candidates (12(=2×6) CCEs), twocandidates (8(=4×2) CCEs), and two candidates (16(=8×2) CCEs),respectively. By this means, each terminal need only perform blinddecoding on CCEs within a search space assigned to that terminal,enabling the number of blind decoding operations to be decreased. Here,a search space of each terminal is set using a terminal ID of eachterminal, and a hash function, which is a function that performsrandomization. This terminal-specific CCE area is called “UE specificSearch Space (UE-SS).”

On the other hand, a PDCCH also includes control information for dataassignment common to terminals simultaneously reported to a plurality ofterminals (e.g., assignment information related to a downlink broadcastsignal and assignment information related to a paging signal)(hereinafter also referred to as “control information for sharedchannels”). In order to transmit control information for sharedchannels, a CCE area (hereinafter also referred to as “Common SearchSpace: C-SS”) common to all terminals that should receive a downlinkbroadcast signal is used for a PDCCH. In C-SS, for CCE aggregationlevels 4 and 8, respectively, there are four candidates (16(=4×4) CCEs)and two candidates (16=(8×2) CCEs), a total of six candidates for CCEssubject to blind decoding.

Furthermore, the terminal performs blind decoding on each of DCI formatsin two sizes in a UE-SS; DCI format (DCI 0/1A) commonly used for allterminals and DCI formats (DCI 1, 2, 2A) dependent on a transmissionmode. For example, the terminal performs 16 blind decoding operationsfor each of PDCCHs in two sizes within a UE-SS. Furthermore, theterminal performs six blind decoding operations described above on eachof DCI format 1C (hereinafter also referred to as “DCI 1C”) which is aformat for shared channel assignment and DCI 1A (that is, a total of 12blind decoding operations).

Here, DCI 1A used for shared channel assignment and DCI 0/1A used forterminal-specific data assignment have the same size and aredistinguished from each other by terminal IDs. Therefore, the basestation can transmit DCI 0/1A for performing terminal-specific dataassignment also with a C-SS without increasing the number of blinddecoding operations by the terminal.

Also, standardization has begun on 3GPP LTE-Advanced (hereinafterreferred to as “LTE-A”), which implements still higher communicationspeeds than LTE. In LTE-A, a maximum downlink transmission speed of 1Gbps or above and a maximum uplink transmission speed of 500 Mbps orabove are implemented, offering the prospect of base stations andterminals (hereinafter referred to as “LTE-A terminals”) capable ofcommunication at a wideband frequency of 40 MHz or above beingintroduced. Also, an LTE-A system is required to accommodate not onlyLTE-A terminals but also terminals compatible with an LTE system(hereinafter referred to as “LTE terminals”).

In LTE-A, a band aggregation method has been proposed whereby aplurality of frequency bands are aggregated in performing communicationin order to implement wideband communication of 40 MHz or above (seeNon-Patent Literature 1, for example). For example, a frequency bandhaving a width of 20 MHz is assumed as a basic communication band unit(hereinafter referred to as a “component band”). Therefore, in LTE-A,for example, a 40 MHz system bandwidth is implemented by aggregating twocomponent bands. Also, both an LTE terminal and an LTE-A terminal can beaccommodated in one component band.

In LTE-A, when data is assigned to a plurality of component bands for acertain terminal, assignment control information is notified through aplurality of PDCCHs. That is, the resource assignment result of aplurality of component bands is notified using one PDCCH for eachcomponent band.

In LTE-A, a transmission method using non-continuous band assignment anda transmission method using MIMO are newly introduced as uplinktransmission methods. As a result, studies are being carried out on adefinition of new DCI formats (e.g., DCI formats 0A, 0B (hereinafteralso referred to as “DCI 0A and 0B”)) (see Non-Patent Literature 4, forexample). That is, DCI 0A and 0B are DCI formats in dependence on anuplink transmission mode.

CITATION LIST Non-Patent Literature

-   NPL 1    -   3GPP TS 36.211 V8.7.0, “Physical Channels and Modulation        (Release 8),” 2009-05-   NPL 2    -   3GPP TS 36.212 V8.7.0, “Multiplexing and channel coding (Release        8),” 2009-05-   NPL 3    -   3GPP TS 36.213 V8.7.0, “Physical layer procedures (Release 8),”        2009-05-   NPL 4    -   3GPP TSG RAN WG1 meeting, R1-092641, “PDCCH design for Carrier        aggregation and Post Rel-8 feature,” June 2009

SUMMARY OF INVENTION Technical Problem

As described above, in LTE-A, when DCI formats in dependence on adownlink transmission mode (DCI 1, 2, 2A), DCI formats in dependence onan uplink transmission mode (DCI 0A, 0B) and a DCI format common to allterminals without depending on any transmission mode (DCI 0/1A) are usedwithin a UE-SS, the terminal performs blind decoding (monitoring) onPDCCHs in the above-described three types of DCI format. For example, asdescribed above, since a UE-SS requires 16 blind decoding operations pertype of DCI format, the blind decoding count within the UE-SS amounts toa total of 48 times (=16 times×3 types). Therefore, when 12 times (=6times×2 types), which is the blind decoding count for two types of DCIformat within a C-SS is added, a total of 60 times of blind decodingoperations are necessary.

Here, when a plurality of component bands are set for one terminal, aC-SS and UE-SS may be set in each component band as described above. Inthis case, the blind decoding count at the terminal becomes enormous,increasing the circuit scale and power consumption of the terminal.When, for example, five component bands are set for one terminal, theterminal requires a total of 300 times (=60 times×5) of blind decodingoperations.

Furthermore, the blind decoding count (that is, the number of CCEcandidates) per component band may be reduced uniformly among aplurality of component bands to reduce the blind decoding count at theterminal. However, CCEs in each component band are used in contentionamong a plurality of terminals. For this reason, when the number ofterminals as assignment targets is large, if the number of CCEcandidates available per terminal decreases, all CCEs within a searchspace may be used for other terminals, increasing a probability(referred to as “CCE block rate”) that terminals can no longer beassigned).

It is an object of the present invention to provide a base station,terminal, CCE assignment method and CCE blind decoding method capable ofreducing a blind decoding count of a terminal without increasing a CCEblock rate even when a plurality of component bands are configured forthe terminal.

Solution to Problem

A base station according to the present invention adopts a configurationincluding a setting section that sets a common search space for a radiocommunication terminal apparatus communicating using a plurality ofcomponent bands and other radio communication terminal apparatuses foreach of the plurality of component bands and sets a specific searchspace for the radio communication terminal apparatus for each of theplurality of component bands, and an assignment section that assignscontrol information addressed to the radio communication terminalapparatus to CCEs within the common search space or CCEs within thespecific search space, wherein the assignment section assigns thecontrol information only to CCEs within the common search space set in aspecific component band or CCEs within the specific search space set inthe specific component band among the plurality of component bands, orassigns the control information only to CCEs within the common searchspace among the common search spaces and the specific search spaces setin the plurality of component bands respectively.

A terminal according to the present invention is a radio communicationterminal apparatus that communicates using a plurality of componentbands and adopts a configuration including a reception section thatreceives control information assigned to a common search space set forthe radio communication terminal apparatus and other radio communicationterminal apparatuses for each of the plurality of component bands and aspecific search space set for the radio communication terminal apparatusfor each of the plurality of component bands, a calculation section thatcalculates the specific search space set in the radio communicationterminal apparatus, and a decoding section that performs blind decodingon CCEs within the common search space or CCEs within the specificsearch space, to obtain the control information for the radiocommunication terminal apparatus, wherein the decoding section performsblind decoding only on CCEs within the common search space set in aspecific component band and CCEs within the specific search space set inthe specific component band among the plurality of component bands orperforms blind decoding only on CCEs within the common search spaceamong the common search spaces and the specific search spaces set in theplurality of component bands respectively.

A CCE assignment method according to the present invention includes asetting step of setting a common search space for a radio communicationterminal apparatus communicating using a plurality of component bandsand other radio communication terminal apparatuses for each of theplurality of component bands and setting a specific search space for theradio communication terminal apparatus for each of the plurality ofcomponent bands, and an assigning step of assigning control informationaddressed to the radio communication terminal apparatus to CCEs withinthe common search space or CCEs within the specific search space,wherein in the assigning step, the control information is assigned onlyto CCEs within the common search space set in a specific component bandor CCEs within the specific search space set in the specific componentband among the plurality of component bands or the control informationis assigned only to CCEs within the common search space among the commonsearch spaces and the specific search spaces set in the plurality ofcomponent bands respectively.

A CCE blind decoding method according to the present invention is a CCEblind decoding method for a radio communication terminal apparatuscommunicating using a plurality of component bands and other radiocommunication terminal apparatuses and includes a receiving step ofreceiving control information assigned to a common search space set ineach of the plurality of component bands and a specific search space setin each of the plurality of component bands for the radio communicationterminal apparatus and the other radio communication terminalapparatuses, a calculating step of calculating the specific search spaceset in the radio communication terminal apparatus, and a decoding stepof blind decoding CCEs within the common search space or CCEs within thespecific search space and thereby obtaining the control informationaddressed to the radio communication terminal apparatus, wherein in thedecoding step, blind decoding is performed only on CCEs within thecommon search space set in a specific component band and CCEs within thespecific search space set in the specific component band among theplurality of component bands or blind decoding is performed only on CCEswithin the common search space among the common search spaces and thespecific search spaces set in the plurality of component bandsrespectively.

Advantageous Effects of Invention

The present invention can reduce a blind decoding count of a terminaleven when a plurality of component bands are set for the terminalwithout increasing a CCE block rate.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram showing a configuration of a base stationaccording to Embodiment 1 of the present invention;

FIG. 2 is a diagram illustrating an example of setting a search spaceaccording to Embodiment 1 of the present invention;

FIG. 3 is a block diagram showing a configuration of a terminalaccording to Embodiment 1 of the present invention;

FIG. 4 is a diagram illustrating CCE assignment processing and blinddecoding (monitoring) processing according to Embodiment 1 of thepresent invention (when one component band is set in the terminal);

FIG. 5 is a diagram illustrating CCE assignment processing and blinddecoding (monitoring) processing according to Embodiment 1 of thepresent invention (when a plurality of component bands are set in theterminal);

FIG. 6 is a diagram illustrating CCE assignment processing and blinddecoding (monitoring) processing according to Embodiment 2 of thepresent invention;

FIG. 7 is a diagram illustrating CCE assignment processing and blinddecoding (monitoring) processing according to Embodiment 3 of thepresent invention; and

FIG. 8 is a diagram illustrating CCE assignment processing and blinddecoding (monitoring) processing according to Embodiment 4 of thepresent invention.

DESCRIPTION OF EMBODIMENTS

Now, embodiments of the present invention will be described in detailwith reference to the accompanying drawings. In the embodiments,identical configuration elements are assigned the same reference codes,and duplicate descriptions thereof are omitted.

Furthermore, in the following descriptions, DCI 1C and 1A will be usedas DCI formats for shared channel assignment, DCI 0/1A will be used as aDCI format for data assignment which is a default transmission modecommonly used for all terminals (usable for terminals in anytransmission mode independently of the transmission mode), DCI 0A and 0Bwill be used as DCI formats for data assignment which depend on anuplink transmission mode and DCI 1, 2, and 2A will be used as DCIformats for data assignment which depend on a downlink transmissionmode.

Embodiment 1

FIG. 1 is a block diagram showing the configuration of base station 100according to this embodiment.

In base station 100 shown in FIG. 1 , component band configurationsection 101 sets (configures) one or a plurality of component bands usedin an uplink and downlink respectively for each terminal, in accordancewith a desired transmission rate or data transmission amount, forexample. Here, component band configuration section 101 configures onecomponent band for an LTE terminal, and configures one or a plurality ofcomponent bands for an LTE-A terminal. Also, component bandconfiguration section 101 configures one component band among aplurality of component bands configured for an LTE-A terminal as ananchor band of that LTE-A terminal. Furthermore, component bandconfiguration section 101 configures respective transmission modes(e.g., spatial multiplexing MIMO transmission, beam formingtransmission, non-continuous band assignment or the like) in the uplinkand downlink for each component band set in each terminal based on achannel situation or the like of each terminal. Then, component bandconfiguration section 101 outputs configuration information includinginformation on the component bands, anchor band and transmission modesconfigured for each terminal to control section 102, search spacesetting section 103, PDCCH generation section 104, andencoding/modulation section 107. The information included in theconfiguration information is reported to each terminal viaencoding/modulation section 107 as upper-layer control information (RRCcontrol information). Furthermore, as the anchor band, for example, acomponent band having a good long-time average channel situation (e.g.,component band with little channel attenuation (path loss)), a componentband with a high SIR, a component band with higher transmission power orreceiving power or a component band with less interference from othercells is selected.

Control section 102 generates assignment control information accordingto the number of component bands shown in the configuration informationinput from component band configuration section 101. For example, for aterminal for which only one component band has been configured, controlsection 102 generates assignment control information including MCSinformation corresponding to one transport block, resource (RB)assignment information, and HARQ information. On the other hand, for aterminal for which a plurality of component bands have been configured,control section 102 generates assignment control information for each ofthe plurality of component bands. Here, as resource assignmentinformation, control section 102 generates uplink resource assignmentinformation indicating an uplink resource (for example, a PUSCH(Physical Uplink Shared Channel)) to which terminal uplink data isassigned, and downlink resource assignment information indicating adownlink resource (for example, a PDSCH (Physical Downlink SharedChannel)) to which downlink data addressed to a terminal is assigned.

Here, control section 102 generates assignment control information (DCI0A, 0B) corresponding to the uplink transmission mode of a terminal,assignment control information (DCI 1, 2 or 2A) corresponding to thedownlink transmission mode or assignment control information (DCI 0/1A)common to all terminals for each terminal and for each component bandbased on the configuration information input from component bandconfiguration section 101.

For example, during normal data transmission, control section 102generates assignment control information (DCI 1, 2, 2A, 0A, 0B)corresponding to a transmission mode of each component band of eachterminal so as to be able to perform data transmission in a transmissionmode set in each terminal to improve throughput. However, depending on adrastic variation in the channel situation or a variation ininterference from a neighboring cell or the like, there can be asituation in which reception errors occur with a high frequency in thetransmission mode set for each terminal. In this case, control section102 generates assignment control information common to all terminals(DCI 0/1A), that is, assignment control information in a defaulttransmission mode, and can thereby realize robuster transmission.

Furthermore, when the channel situation deteriorates, control section102 also generates assignment control information common to allterminals (DCI 0/1A) during transmission of control information (RRCsignaling) of an upper layer to report a change of the transmissionmode. Here, the number of information bits of DCI 0/1A common to allterminals is smaller than the number of information bits of DCI 1, 2, 2A0A, 0B in dependence on the transmission mode. For this reason, when thesame number of CCEs is set, DCI 0/1A can transmit data at a lower codingrate than DCI 1, 2, 2A 0A, 0B. Therefore, when the channel situationdeteriorates, control section 102 uses DCI 0/1A, and even a terminal ina poor channel situation can thereby receive data at a high error rate.

Furthermore, control section 102 generates assignment controlinformation for shared channels (e.g., DCI 1C, 1A) for data assignmentcommon to a plurality of terminals such as broadcast information andpaging information in addition to assignment control information forterminal-specific data assignment.

Then, control section 102 outputs MCS information and HARQ informationout of the generated assignment control information forterminal-specific data assignment to PDCCH generation section 104,outputs uplink resource assignment information to PDCCH generationsection 104 and extraction section 117, and outputs downlink resourceassignment information to PDCCH generation section 104 and multiplexingsection 109. Furthermore, control section 102 outputs the generatedassignment control information for shared channels to PDCCH generationsection 104.

Search space setting section 103 sets a common search space (C-SS) whichis a search space common to all terminals and a specific search space(UE-SS) which is a search space specific to each terminal. Specifically,search space setting section 103 sets CCEs set beforehand in eachcomponent band (e.g., 16 CCEs from the first CCE) as a C-SS. Here, asassignment candidates within a C-SS made up of 16 CCEs, there are fourcandidates for a PDCCH having four CCEs and two candidates for a PDCCHhaving eight CCEs, a total of six candidates. Furthermore, search spacesetting section 103 sets a UE-SS for each component band set in eachterminal based on information on a component band set in each terminalindicated by the configuration information input from component bandconfiguration section 101. For example, search space setting section 103calculates a UE-SS in a component band set in a certain terminal fromCCE numbers calculated using a terminal ID of the terminal and a hashfunction for executing randomization, and the number of CCEs (L) makingup a search space. A setting example of a C-SS and UE-SS correspondingto a certain terminal is shown in FIG. 2 . In FIG. 2 , search spacesetting section 103 sets four candidates (CCE0 to 3, CCE4 to 7, CCE8 to11, CCE12 to 15) for CCE aggregation level 4 and two candidates (CCE0 to7, CCE8 to 15) for CCE aggregation level 8, a total of six candidates asa C-SS. Furthermore, as shown in FIG. 2 , search space setting section103 sets six candidates (CCE16 to 21) for CCE aggregation level 1, sixcandidates (CCE6 to 17) for CCE aggregation level 2, two candidates(CCE20 to 23, CCE24 to 27) for CCE aggregation level 4 and twocandidates (CCE16 to 23, CCE24 to 31) for CCE aggregation level 8, atotal of 16 candidates as a UE-SS. Search space setting section 103 setsa UE-SS for each set component band for an LTE-A terminal for which aplurality of component bands are set. Search space setting section 103then outputs search space information indicating set UE-SSs of eachterminal to assignment section 106.

PDCCH generation section 104 generates a PDCCH signal includingassignment control information for terminal-specific data assignmentsuch as uplink resource assignment information, downlink resourceassignment information, MCS information, and HARQ information input fromcontrol section 102 or a PDCCH signal including assignment controlinformation for shared channels such as broadcast information common toterminals and paging information. At this time, PDCCH generation section104 adds CRC bits to uplink resource assignment information and downlinkresource assignment information, and also masks (or scrambles) CRC bitswith a terminal ID in generating a PDCCH signal. Then, PDCCH generationsection 104 outputs a masked PDCCH signal to encoding/modulation section105.

Encoding/modulation section 105 modulates a PDCCH signal input fromPDCCH generation section 104 after channel encoding, and outputs amodulated PDCCH signal to assignment section 106. Here,encoding/modulation section 105 sets a coding rate so that adequatereception quality is obtained by each terminal, based on channel qualityinformation (a CQI: Channel Quality Indicator) notified from eachterminal. For example, the nearer the location of a terminal to a cellboundary (the poorer the channel quality of a terminal), the lower isthe coding rate set by encoding/modulation section 105.

Assignment section 106 assigns a PDCCH signal including assignmentcontrol information for shared channels input from encoding/modulationsection 105 and a PDCCH signal including assignment control informationfor terminal-specific data assignment for each terminal to CCEs within aC-SS indicated by search space information input from search spacesetting section 103 or CCEs within a UE-SS for each terminalrespectively. Here, the CCE aggregation level of one PDCCH signaldiffers according to the coding rate and the number of bits (amount ofassignment control information) of the PDCCH signal. For example, sincethe coding rate of a PDCCH signal addressed to a terminal located in thevicinity of a cell boundary is set low, and more physical resources arenecessary, assignment section 106 assigns a PDCCH signal addressed to aterminal located in the vicinity of a cell boundary to a greater numberof CCEs.

For example, assignment section 106 selects one assignment candidatefrom among assignment candidates within a C-SS (e.g., FIG. 2 ).Assignment section 106 then assigns a PDCCH signal including assignmentcontrol information for shared channels to CCEs within the selectedcandidate.

Furthermore, for a terminal for which only one component band isconfigured, assignment section 106 assigns a PDCCH signal to CCEs withinthe UE-SS set in the terminal within the configured component band whenassignment control information for terminal-specific data assignmentincluded in the PDCCH signal addressed to the terminal is atransmission-mode-dependent DCI format (e.g., DCI 1, 2, 2A 0A, 0B). Onthe other hand, when assignment control information forterminal-specific data assignment included in the PDCCH signal addressedto the terminal is a format common to all terminals (e.g., DCI 0/1A),assignment section 106 assigns the PDCCH signal to CCEs within a C-SS ofthe configured component band or CCEs within a UE-SS configured for theterminal.

Furthermore, for a terminal for which a plurality of component bands areset, assignment section 106 assigns the PDCCH signal to CCEs within theUE-SS set in the terminal in each component band when the assignmentcontrol information for terminal-specific data assignment included inthe PDCCH signal addressed to the terminal is atransmission-mode-dependent DCI format (e.g., DCI 1, 2, 2A, 0A, 0B). Inthis case, assignment section 106 assigns assignment control informationto CCEs within the component band in which data subject to resourceassignment indicated by the assignment control information istransmitted. On the other hand, when assignment control information forterminal-specific data assignment included in the PDCCH signal addressedto the terminal is a format common to all terminals (e.g., DCI 0/1A),assignment section 106 assigns the PDCCH signal only to CCEs within aC-SS set in an anchor band (specific component band) among a pluralityof component bands configured for the terminal or CCEs within a UE-SSset in the terminal in an anchor band (specific component band).

Then assignment section 106 outputs a PDCCH signal assigned to a CCE tomultiplexing section 109. Also, assignment section 106 outputsinformation indicating a CCE to which a PDCCH signal has been assignedto ACK/NACK reception section 120. Details of CCE assignment processingperformed by assignment section 106 will be given later herein.

Encoding/modulation section 107 modulates configuration informationinput from component band configuration section 101 after channelencoding, and outputs modulated configuration information tomultiplexing section 109.

Encoding/modulation section 108 modulates input transmission data(downlink data) after channel encoding, and outputs a modulatedtransmission data signal to multiplexing section 109.

Multiplexing section 109 multiplexes a PDCCH signal input fromassignment section 106, configuration information input fromencoding/modulation section 107, and a data signal (that is, a PDSCHsignal) input from encoding/modulation section 108. Here, multiplexingsection 109 maps a PDCCH signal and data signal (PDSCH signal) to eachdownlink component band based on downlink resource assignmentinformation input from control section 102. Multiplexing section 109 mayalso map the configuration information to a PDSCH. Then, multiplexingsection 109 outputs a multiplex signal to IFFT (Inverse Fast FourierTransform) section 110.

IFFT section 110 converts a multiplex signal input from multiplexingsection 109 to a time waveform, and CP (Cyclic Prefix) addition section111 obtains an OFDM signal by adding a CP to this time waveform.

Radio transmission section 112 executes transmission radio processing(up-conversion, digital/analog (D/A) conversion, and so forth) on anOFDM signal input from CP addition section 111, and transmits theresulting signal via antenna 113.

On the other hand, radio reception section 114 executes radio receptionprocessing (down-conversion, analog/digital (A/D) conversion, and soforth) on a received radio signal received in a reception band viaantenna 113, and outputs the obtained received signal to CP removalsection 115.

CP removal section 115 removes a CP from the received signal, and FFT(Fast Fourier Transform) section 116 converts the received signalwithout a CP to a frequency-domain signal.

Extraction section 117 extracts uplink data from a frequency-domainsignal input from FFT section 116 based on uplink resource assignmentinformation input from control section 102, and IDFT (Inverse DiscreteFourier Transform) section 118 converts an extracted signal to atime-domain signal, and outputs that time-domain signal to datareception section 119 and ACK/NACK reception section 120.

Data reception section 119 decodes a time-domain signal input from IDFTsection 118. Then, data reception section 119 outputs decoded uplinkdata as received data.

Of the time-domain signal input from IDFT section 118, ACK/NACKreception section 120 extracts an ACK/NACK signal from each terminalcorrespond to downlink data (a PDSCH signal) from an uplink controlchannel (for example, a PUCCH (Physical Uplink Control Channel))associated with a CCE used for assignment of that downlink data, basedon information input from assignment section 106 and ACK/NACK receptionsection 120 performs ACK/NACK determination for an extracted ACK/NACKsignal. Here, a CCE and PUCCH are associated in order to make efficientuse of downlink channel communication resources by eliminating the needfor signaling for notifying a PUCCH used by a terminal for ACK/NACKsignal transmission from a base station to each terminal. Therefore,each terminal determines a PUCCH to use for transmission of an ACK/NACKsignal from that terminal from a CCE to which control information (aPDCCH signal) to that terminal is mapped in accordance with thisassociation. Here, when base station 100 assigns a PDCCH signal thatincludes downlink resource assignment information of downlink data (aPDSCH signal) of a plurality of component bands to a CCE of a downlinkcomponent band of a plurality of component bands, ACK/NACK receptionsection 120 extracts a plurality of ACK/NACK signals from a PUCCHassociated with the CCE number of each CCE.

FIG. 3 is a block diagram showing the configuration of terminal 200according to this embodiment. Terminal 200 is an LTE-A terminal, andreceives a data signal (downlink data) using a plurality of downlinkcomponent bands, and transmits an ACK/NACK signal for that data signalto base station 100 using a PUCCH of one uplink component band.

In terminal 200 shown in FIG. 3 , radio reception section 202 isconfigured so as to enable a change of reception band, and changes areception band based on band information input from configurationinformation reception section 206. Then the radio reception section 202executes radio reception processing (down-conversion, analog/digital(A/D) conversion, and so forth) on a received radio signal (here, anOFDM signal) received in a reception band via antenna 201, and outputsthe obtained received signal to CP removal section 203. The receivedsignal includes control information of an upper layer including a PDSCHsignal, PDCCH signal and configuration information. Furthermore, thePDCCH signal (assignment control information) is assigned to a commonsearch space (C-SS) set in terminal 200 and other terminals for eachcomponent band or specific search space (UE-SS) in terminal 200 for eachcomponent band.

CP removal section 203 removes a CP from the received signal, and FFTsection 204 converts the received signal without a CP to afrequency-domain signal. This frequency-domain signal is output toseparation section 205.

Separation section 205 separates a signal input from FFT section 204into an upper-layer control signal that includes configurationinformation (for example, RRC signaling or the like), a PDCCH signal,and a data signal (that is, a PDSCH signal). Then, separation section205 outputs a control signal to configuration information receptionsection 206, outputs a PDCCH signal to PDCCH reception section 207, andoutputs a PDSCH signal to PDSCH reception section 208.

Configuration information reception section 206 reads informationindicating an uplink component band and downlink component bandconfigured for this terminal from a control signal input from separationsection 205, and outputs the read information to PDCCH reception section207, the radio reception section 202, and a radio transmission section215 as band information. Also, configuration information receptionsection 206 reads information indicating a terminal ID set for thisterminal from a control signal input from separation section 205, andoutputs the read information to PDCCH reception section 207 as terminalID information. Furthermore, configuration information reception section206 reads information indicating an anchor band configured for thisterminal, and outputs the read information to PDCCH reception section207 as anchor band information. Furthermore, configuration informationreception section 206 reads information indicating a transmission modeconfigured for this terminal, and outputs the read information to PDCCHreception section 207 as transmission mode information.

PDCCH reception section 207 performs blind decoding (monitoring) of aPDCCH signal input from separation section 205, and obtains a PDCCHsignal addressed to this terminal. Here, PDCCH reception section 207performs blind decoding on a DCI format for data assignment common toall terminals (e.g., DCI 0/1A), a transmission-mode-dependent DCI format(e.g., DCI 1, 2, 2A 0A, 0B) configured for this terminal and a DCIformat for shared channel assignment common to all terminals (e.g., DCI1C, 1A), and thereby obtains a PDCCH signal including assignment controlinformation in each DCI format.

Specifically, PDCCH reception section 207 performs blind decoding of aDCI format for shared channel assignment (DCI 1C, 1A) and a DCI formatfor data assignment common to all terminals (DCI 0/1A) for a C-SS of ananchor band indicated in anchor band information input fromconfiguration information reception section 206. That is, PDCCHreception section 207 demodulates and decodes CCE candidates of each CCEaggregation level within a C-SS focused on the size of a DCI format forshared channel assignment and the size of a DCI format for dataassignment common to all terminals. PDCCH reception section 207 demasksthe CRC bit with an ID common to a plurality of terminals for thedecoded PDCCH signal, and thereby determines that a PDCCH signalresulting in CRC=OK (no error) is a PDCCH signal including assignmentcontrol information for shared channels. Furthermore, PDCCH receptionsection 207 demasks the CRC bit with the terminal ID of this terminalindicated by terminal ID information for the decoded PDCCH signal, andthereby determines that a PDCCH signal resulting in CRC=OK (no error) isa PDCCH signal including assignment control information for dataassignment common to all terminals. That is, PDCCH reception section 207distinguishes whether the assignment control information of DCI 0/1A ina C-SS is for shared channels or for data assignment, with a terminal ID(common ID for a plurality of terminals or terminal ID of terminal 200).

Furthermore, when the number of downlink component bands indicated byband information input from configuration information reception section206 is one, PDCCH reception section 207 calculates a UE-SS of thisterminal for each CCE aggregation level using the terminal ID of thisterminal indicated by the terminal ID information input fromconfiguration information reception section 206. PDCCH reception section207 then demodulates and decodes CCE candidates of each calculated CCEaggregation level in a UE-SS focused on the size of a DCI formatcorresponding to a transmission mode (transmission mode indicated intransmission mode information) set in this terminal and the size of aDCI format common to all terminals (DCI 0/1A). PDCCH reception section207 demasks the CRC bit with the terminal ID of this terminal for thedecoded PDCCH signal, and thereby determines that the PDCCH signalresulting in CRC=OK (no error) is a PDCCH signal addressed to thisterminal.

On the other hand, when the number of downlink component bands indicatedby the band information input from configuration information receptionsection 206 is plural, PDCCH reception section 207 calculates a UE-SS ofthis terminal for each CCE aggregation level using the terminal ID ofthis terminal indicated by terminal ID information input fromconfiguration information reception section 206 in each configuredcomponent band. PDCCH reception section 207 demodulates and decodes CCEcandidates at each calculated CCE aggregation level within a UE-SSfocused on the size of a DCI format corresponding to a transmission modeset in this terminal and the size of a DCI format common to allterminals (DCI 0/1A) in an anchor band indicated by anchor bandinformation. Furthermore, PDCCH reception section 207 demodulates anddecodes CCE candidates at each calculated CCE aggregation level within aUE-SS focused on only the size of a DCI format corresponding to thetransmission mode set in the terminal in component bands other than theanchor band among a plurality of component bands configured for thisterminal.

That is, PDCCH reception section 207 performs blind decoding only onCCEs within a C-SS set in an anchor band (specific component band) amonga plurality of component bands configured for this terminal and CCEswithin a UE-SS set in this terminal in the anchor band (specificcomponent band). PDCCH reception section 207 then demasks the CRC bitwith the terminal ID of this terminal for the decoded PDCCH signal, andthereby determines that the PDCCH signal resulting in CRC=OK (no error)as a PDCCH signal addressed to this terminal.

PDCCH reception section 207 then outputs the downlink resourceassignment information included in the PDCCH signal addressed to thisterminal to PDSCH reception section 208 and outputs the uplink resourceassignment information to mapping section 212. Furthermore, PDCCHreception section 207 outputs a CCE number of a CCE from which a PDCCHsignal addressed to this terminal is detected (a CCE resulting inCRC=OK) (CCE number of the first CCE when the CCE aggregation level isplural) to mapping section 212. Details of the blind decoding(monitoring) processing by PDCCH reception section 207 will be describedlater.

PDSCH reception section 208 extracts received data (downlink data) froma PDSCH signal input from separation section 205 based on the downlinkresource assignment information input from PDCCH reception section 207.Also, PDSCH reception section 208 performs error detection on theextracted received data (downlink data). Then, PDSCH reception section208 generates a NACK signal as an ACK/NACK signal if the result of errordetection is that there is an error in the received data, or generatesan ACK signal as an ACK/NACK signal if the result of error detection isthat there is no error in the received data, and outputs an ACK/NACKsignal to modulation section 209.

Modulation section 209 modulates an ACK/NACK signal input from PDSCHreception section 208, and outputs a modulated ACK/NACK signal to DFT(Discrete Fourier transform) section 211.

Modulation section 210 modulates transmission data (uplink data), andoutputs a modulated data signal to DFT section 211.

DFT section 211 converts an ACK/NACK signal input from modulationsection 209 and a data signal input from modulation section 210 to thefrequency domain, and outputs an obtained plurality of frequencycomponents to mapping section 212.

Mapping section 212 maps a frequency component corresponding to a datasignal, from among a plurality of frequency components input from DFTsection 211, to a PUSCH placed in an uplink component band, inaccordance with uplink resource assignment information input from PDCCHreception section 207. Also, mapping section 212 maps a frequencycomponent or code resource corresponding to an ACK/NACK signal, fromamong a plurality of frequency components input from DFT section 211, toa PUCCH placed in an uplink component band, in accordance with a CCEnumber input from PDCCH reception section 207.

Modulation section 209, modulation section 210, DFT section 211, andmapping section 212 may also be provided for each component band.

IFFT section 213 converts a plurality of frequency components mapped toa PUSCH to a time-domain waveform, and CP addition section 214 adds a CPto that time-domain waveform.

Radio transmission section 215 is configured so as to enable a change oftransmission band, and sets a transmission band based on bandinformation input from configuration information reception section 206.Then, the radio transmission section 215 executes transmission radioprocessing (up-conversion, digital/analog (D/A) conversion, and soforth) on a signal with a CP, and transmits the resulting signal viaantenna 201.

A detailed description will now be given of PDCCH signal assignmentprocessing performed by assignment section 106 of base station 100, andblind decoding (monitoring) processing performed by PDCCH receptionsection 207 of terminal 200.

In the following description, component band configuration section 101(FIG. 1 ) of base station 100 configures one downlink component band forterminal 200 (LTE-A terminal) as shown in FIG. 4 and configures aplurality of downlink component bands (component bands 1, 2, . . . ) asshown in FIG. 5 . Also, component band configuration section 101configures component band 1 as an anchor band of terminal 200.

In the following description, a PDCCH placed in each downlink componentband is constructed of a plurality of CCEs as shown in FIG. 4 and FIG. 5. Furthermore, in FIG. 4 and

FIG. 5 , base station 100 assumes that the number of CCEs making up aC-SS set in each component band is four and the number of CCEs making upa UE-SS of each component band set in terminal 200 is six. That is,search space setting section 103 of base station 100 sets a C-SS made upof four CCEs in each component band and sets a UE-SS made up of six CCEsin each component band as shown in FIG. 4 and FIG. 5 . Furthermore, asshown in FIG. 4 and FIG. 5 , terminal 200 sets the C-SS according toinformation reported from base station 100 beforehand and alsocalculates the UE-SS of this terminal shown in FIG. 5 based on theterminal ID of this terminal.

First, a case will be described where the number of component bandsconfigured for terminal 200 is one (FIG. 4 ).

In this case, assignment section 106 of base station 100 assigns a PDCCHsignal including assignment control information for shared channels (DCI1C, 1A) to CCEs in the C-SS shown in FIG. 4 . Alternatively, assignmentsection 106 assigns a PDCCH signal including assignment controlinformation for data assignment common to all terminals (DCI 0/1A) toCCEs in the C-SS or CCEs in the UE-SS shown in FIG. 4 . Alternatively,assignment section 106 assigns transmission-mode-dependent assignmentcontrol information set in terminal 200 (uplink (DCI 0A, 0B), downlink(DCI 1, 2, 2A)) to CCEs in the UE-SS shown in FIG. 4 .

On the other hand, PDCCH reception section 207 of terminal 200 performsblind decoding on a PDCCH signal including assignment controlinformation for shared channels (DCI 1C, 1A) and a PDCCH signalincluding assignment control information for data assignment common toall terminals (DCI 0/1A) or the C-SS shown in FIG. 4 . Furthermore,PDCCH reception section 207 performs blind decoding on a PDCCH signalincluding transmission-mode-dependent assignment control information(uplink (assignment control information in which any one of DCIs 0A and0B is set), downlink (assignment control information in which any one ofDCI 1, 2 and 2A is set) and a PDCCH signal including assignment controlinformation for data assignment common to all terminals (DCI 0/1A) forthe UE-SS shown in FIG. 4 .

That is, terminal 200 performs blind decoding on two types of DCI format(DCI 1C and DCI 0/1A) for the C-SS and performs blind decoding on threetypes of DCI format (uplink transmission-mode-dependent DCI (DCI of anyone of DCIs 0A and 0B) and downlink transmission-mode-dependent DCI (DCIof any one of DCI 1, 2 and 2A) and DCI 0/1A)) for the UE-SS in thecomponent bands shown in FIG. 4 □ For example, a case will be describedwhere blind decoding is performed six times for each DCI format for theC-SS and blind decoding is performed 16 times for each DCI format forthe UE-SS as shown in FIG. 2 . In this case, PDCCH reception section 207of terminal 200 performs blind decoding a total of 60 (=(6×2)+(16×3))times in the component band shown in FIG. 4 .

Next, a case will be described where a plurality of component bands areconfigured for terminal 200 (FIG. 5 ).

In this case, assignment section 106 of base station 100 assigns a PDCCHsignal including assignment control information for shared channels (DCI1C, 1A) to CCEs within a C-SS of component band 1 (anchor band) shown inFIG. 5 . Alternatively, assignment section 106 assigns a PDCCH signalincluding assignment control information for data assignment common toall terminals (DCI 0/1A) to CCEs in a C-SS of component band 1 (anchorband) shown in FIG. 5 or CCEs in a UE-SS of component band 1 (anchorband). Furthermore, assignment section 106 assignstransmission-mode-dependent assignment control information set interminal 200 (uplink (DCI 0A, 0B), downlink (DCI 1, 2, 2A)) to CCEs ineach UE-SS of a plurality of component bands (component bands 1, 2, . .. ) shown in FIG. 5 . For example, assignment section 106 assigns aPDCCH signal including assignment control information indicatingresource assignment information for data transmitted in component band nshown in FIG. 5 to CCEs in a UE-SS of component band n.

That is, when a plurality of component bands are set in terminal 200,base station 100 transmits a PDCCH signal including assignment controlinformation for data assignment common to all terminals (DCI 0/1A) onlyusing a C-SS or UE-SS in the anchor band (component band 1 in FIG. 5 )of terminal 200. Furthermore, base station 100 transmits a PDCCH signalincluding assignment control information for shared channels (DCI 1C,1A) only using a C-SS in the anchor band (component band 1 in FIG. 5 )of terminal 200. In other words, base station 100 transmits onlytransmission-mode-dependent assignment control information (DCI 1, 2, 2A0A, 0B) in component bands (component bands from component band 2 onwardin FIG. 5 ) other than the anchor band of terminal 200 (component band 1in FIG. 5 ).

On the other hand, PDCCH reception section 207 of terminal 200 performsblind decoding on a PDCCH signal including assignment controlinformation for shared channels (DCI 1C, 1A) and a PDCCH signalincluding assignment control information for data assignment common toall terminals (DCI 0/1A) for the C-SS of component band 1 (anchor band)shown in FIG. 5 . Furthermore, PDCCH reception section 207 performsblind decoding on a PDCCH signal including transmission-mode-dependentassignment control information (uplink (DCI 0A, 0B), downlink (DCI 1, 2,2A)) and a PDCCH signal including assignment control information fordata assignment common to all terminals (DCI 0/1A) for the UE-SS ofcomponent band 1 (anchor band) shown in FIG. 5 . Furthermore, PDCCHreception section 207 performs blind decoding on a PDCCH signalincluding transmission-mode-dependent assignment control information(uplink (DCI 0A, 0B), downlink (DCI 1, 2, 2A)) for UE-SSs of componentbands from component band 2 onward shown in FIG. 5 (that is, componentbands other than the anchor band among a plurality of component bandsconfigured for terminal 200).

That is, PDCCH reception section 207 performs blind decoding(monitoring) on neither a PDCCH signal including assignment controlinformation for shared channels in component bands from component band 2onward shown in FIG. 5 (component bands other than the anchor band) (DCI1C, 1A) nor a PDCCH signal including assignment control information fordata assignment common to all terminals (DCI 0/1A). That is, PDCCHreception section 207 performs blind decoding (monitoring) in both aC-SS and UE-SS in component band 1 (anchor band) shown in FIG. 5 ,whereas in component bands from component band 2 onward (component bandsother than component band 1), PDCCH reception section 207 performs blinddecoding (monitoring) not in a C-SS but only in a UE-SS.

Specifically, terminal 200 has two types of DCI formats (DCI 1C and DCI0/1A) subject to blind decoding (monitoring) in a C-SS of component band1 (anchor band) shown in FIG. 5 . On the other hand, there are threetypes of DCI formats subject to blind decoding (monitoring) in a UE-SSof component band 1 shown in FIG. 5 (uplink transmission-mode-dependentDCI (DCI 0A, 0B) and downlink transmission-mode-dependent DCI (DCI 1, 2,2A) and DCI 0/1A). On the other hand, there is no DCI format subject toblind decoding (monitoring) in C-SSs of component bands from componentband 2 onward shown in FIG. 5 . Furthermore, there are two types of DCIformats subject to blind decoding (monitoring) in UE-SSs of componentbands from component band 2 onward shown in FIG. 5 (uplinktransmission-mode-dependent DCI (DCI 0A, 0B) and downlinktransmission-mode-dependent DCI (DCI 1, 2, 2A)).

Regarding the reduction of a blind decoding count, a case will bedescribed where as shown, for example, in FIG. 2 , blind decoding isperformed six times for each DCI format in a C-SS and blind decoding isperformed 16 times for each DCI format in a UE-SS. In this case, PDCCHreception section 207 performs blind decoding a total of 60(=(6×2)+(16×3)) times in component band 1 (anchor band) and a total of32 (=16×2) times per component band in component bands from componentband 2 onward. That is, in each component band from component band 2onward shown in FIG. 5 , it is possible to reduce the blind decodingcount (a total of 28 times) by a blind decoding count (12(=6×2) times)corresponding to two types of DCI format (DCI 1C, 0/1A) in a C-SS and bya blind decoding count (16 times) corresponding to one type of DCIformat (DCI 0/1A) in a UE-SS.

For example, when five component bands are configured for terminal 200,terminal 200 needs to perform blind decoding a total of 300 times (60times×5) as described above when performing blind decoding on the fivetypes of DCI format in all component bands. By contrast, the presentembodiment needs to perform blind decoding a total of 188 times (=(60times×1)+(32 times×4)). That is, the present embodiment reduces theblind decoding count by 112 times (=28 times×4).

Thus, for terminal 200 for which a plurality of component bands areconfigured, base station 100 assigns assignment control informationcommon to all terminals (DCI 0/1A) only to a C-SS or UE-SS set in theanchor band (component band 1 in FIG. 5 ) among the plurality ofcomponent bands. Thus, terminal 200 needs to perform blind decoding(monitoring) on assignment control information common to all terminals(DCI 0/1A) in only a C-SS and UE-SS set in the anchor band (componentband 1 in FIG. 5 ) among the plurality of component bands configured forthis terminal. That is, terminal 200 does not need to perform blinddecoding (monitoring) on assignment control information common to allterminals (DCI 0/1A) in component bands other than the anchor bandconfigured for this terminal, and can thereby reduce the blind decodingcount in terminal 200.

Similarly, base station 100 assigns assignment control information forshared channels (DCI 1C, 1A) of a plurality of component bandsconfigured for terminal 200 only to a C-SS of the anchor band (componentband 1 in FIG. 5 ) configured for terminal 200. Thus, terminal 200 needsonly to perform blind decoding (monitoring) on assignment controlinformation for shared channels (DCI 1C, 1A) in only a C-SS of theanchor band (component band 1 in FIG. 5 ) configured for this terminal.That is, terminal 200 does not need to perform blind decoding(monitoring) on assignment control information for shared channels (DCI1C, 1A) in component bands other than the anchor band configured forthis terminal, and can thereby reduce the blind decoding count interminal 200.

Here, DCI 0/1A is mainly used, when the channel situation drasticallychanges, to report the change or the like in the transmission mode. Thatis, DCI 0/1A is used, when the channel situation changes for the worseand can no longer communicate in the current transmission mode, toassign control information of an upper layer to which the change to atransmission mode in which communication can be performed even in thatpoor channel situation (that is, an emergency-evacuation-liketransmission mode) is reported. Such control information may betransmitted in any one of a plurality of less frequently used componentbands configured for the terminal. Therefore, even when base station 100assigns assignment control information of DCI 0/1A only to the anchorband, the possibility of the assignment control information of DCI 0/1Abeing simultaneously transmitted is low and the probability of the CCEblock rate increasing due to contention of CCEs with other terminals islow.

Furthermore, base station 100 may configure a component band having agood channel situation (e.g., component band having low channelattenuation (path loss) or component band having a small amount ofinterference from other cells) in the anchor band. This allows basestation 100 to transmit a PDCCH signal including assignment controlinformation of DCI 0/1A and data subject to resource assignmentindicated by the assignment control information (e.g., controlinformation of an upper layer to which a change to anemergency-evacuation-like transmission mode is reported) in a componentband having a good channel situation, allowing robuster transmission.That is, base station 100 configures a component band having a goodchannel situation in the anchor band, and can thereby realize highlyefficient transmission by reducing the error rate of the PDCCH signaland data, and transmitting the signal and data at a high coding rate.

Thus, according to the present embodiment, for terminals for which aplurality of component bands are configured, the base station assignsassignment control information of DCI 0/1A only to the anchor bandconfigured for each terminal. Thus, the terminal needs only to performblind decoding on DCI 0/1A in only the anchor band. This eliminates theneed for the terminal to perform blind decoding on DCI 0/1A in componentbands other than the anchor band among a plurality of component bandsconfigured for this terminal. Furthermore, the assignment controlinformation reported using DCI 0/1A (e.g., control information of anupper layer) is less frequently used than thetransmission-mode-dependent DCI format and may be assigned to any onecomponent band. Therefore, even when the search space to whichassignment control information reported using DCI 0/1A is assigned islimited, the probability of the CCE block rate increasing due tocontention of CCEs with other terminals is low. Therefore, even when aplurality of component bands are configured for the terminal, thepresent embodiment can reduce the blind decoding count of the terminalwithout increasing the CCE block rate.

Embodiment 2

The present embodiment differs from Embodiment 1 in that indicationinformation for indicating a component band subject to resourceassignment is added to assignment control information assigned to aUE-SS of an anchor band of assignment control information of DCI 0/1Afor a terminal for which a plurality of component bands are configured.

The present embodiment will now be explained in detail. Base station 100(FIG. 1 ) and terminal 200 (FIG. 3 ) according to this embodiment havethe same kind of configurations as in Embodiment 1, but the operation ofcontrol section 102, assignment section 106 and PDCCH reception section207 differs.

Furthermore, in the following descriptions, as shown in FIG. 6 ,component band configuration section 101 (FIG. 1 ) of base station 100configures a plurality of downlink component bands (component bands 1,2, . . . ) for terminal 200 (LTE-A terminal) as in the case ofEmbodiment 1 (FIG. 5 ). Furthermore, as shown in FIG. 6 , component bandconfiguration section 101 configures component band 1 as an anchor bandof terminal 200. Furthermore, in FIG. 6 , base station 100 assumes thatthe number of CCEs making up a C-SS to be set in each component band isfour and the number of CCEs making up a UE-SS of each component band tobe set in terminal 200 is six as in the case of Embodiment 1 (FIG. 5 ).

When generating assignment control information of DCI 0/1A for aterminal for which a plurality of component bands are configured,control section 102 of base station 100 (FIG. 1 ) according to thepresent embodiment adds a component band indication bit (CarrierIndicator: CI) which is indication information that indicates acomponent band subject to assignment of resource assignment informationindicated by assignment control information among the plurality ofcomponent bands.

Here, a PDCCH signal including assignment control information for sharedchannels (DCI 1A) is also received by an LTE terminal in addition toterminal 200 (LTE-A terminal). Therefore, when DCI 1A is used asassignment control information for shared channels, a CI cannot be addedto the assignment control information. Furthermore, with assignmentcontrol information for terminal-specific data assignment (DCI 0/1A),the size of assignment control information with a CI is different fromthe size of assignment control information without a CI. That is, whenbase station 100 assigns assignment control information with a CI (forterminal-specific data assignment) and assignment control informationwithout a CI (e.g., for shared channels) within the same C-SS, terminal200 needs to perform blind decoding on DCI 0/1A focused on differentsizes. Therefore, assigning assignment control information (DCI 0/1A)with a CI within a C-SS causes the blind decoding count to increase.

Thus, when assignment control information included in the PDCCH signalfor a terminal for which a plurality of component bands are configuredis a DCI format common to all terminals (DCI 0/1A) and a CI is addedthereto, assignment section 106 assigns the PDCCH signal to CCEs withina UE-SS in the anchor band configured for the terminal. That is, whenassignment control information included in the PDCCH signal is a DCIformat common to all terminals (DCI 0/1A) and a CI is added thereto,assignment section 106 does not assign the PDCCH signal to CCEs within aC-SS. Specifically, assignment section 106 assigns a PDCCH signalincluding assignment control information with a CI (DCI 0/1A (with aCI)) among PDCCH signals including assignment control information fordata assignment common to all terminals (DCI 0/1A) to CCEs within theUE-SS in component band 1 (anchor band) shown in FIG. 6 . Furthermore,assignment section 106 assigns a PDCCH signal including assignmentcontrol information without a CI (DCI 0/1A (without a CI)) to CCEswithin the C-SS in component band 1 (anchor band) shown in FIG. 6 .

Furthermore, assignment section 106 assigns a PDCCH signal includingassignment control information for shared channels (DCI 1C, 1A shown inFIG. 6 ) to CCEs within a C-SS of component band 1 (anchor band) as inthe case of Embodiment 1. Furthermore, assignment section 106 assignstransmission-mode-dependent assignment control information (uplink (DCI0A, 0B), downlink (DCI 1, 2, 2A)) configured for terminal 200 to CCEs ineach UE-SS of a plurality of component bands (component bands 1, 2, . .. shown in FIG. 6 ) configured for terminal 200 as in the case ofEmbodiment 1.

On the other hand, PDCCH reception section 207 of terminal 200 (FIG. 3 )demodulates and decodes CCE candidates at each CCE aggregation levelwithin a UE-SS calculated in the anchor band of this terminal indicatedby the anchor band information focused on the size of a DCI formatcorresponding to the transmission mode set in this terminal and focusedon the size of a DCI format common to all terminals (DCI 0/1A).Specifically, PDCCH reception section 207 performs blind decoding on aPDCCH signal including assignment control information for sharedchannels (DCI 1C, 1A) and a PDCCH signal including assignment controlinformation for data assignment common to all terminals (DCI 0/1A(without a CI)) for the C-SS of component band 1 (anchor band) shown inFIG. 6 as in the case of Embodiment 1. Furthermore, PDCCH receptionsection 207 performs blind decoding on a PDCCH signal includingtransmission-mode-dependent assignment control information (uplink (DCI0A, 0B), downlink (DCI 1, 2, 2A)) for each UE-SS of a plurality ofcomponent bands (component bands 1, 2, . . . shown in FIG. 6 )configured for this terminal as in the case of Embodiment 1.

Furthermore, PDCCH reception section 207 performs blind decoding on aPDCCH signal including assignment control information for dataassignment common to all terminals (DCI 0/1A (with a CI)) for the UE-SSof component band 1 (anchor band) shown in FIG. 6 . At this time, PDCCHreception section 207 performs blind decoding focused on the size ofassignment control information with a CI. That is, PDCCH receptionsection 207 performs blind decoding on CCEs in the UE-SS of componentband 1 shown in FIG. 6 and thereby obtains assignment controlinformation with a CI.

Thus, assignment section 106 of base station 100 adds a CI to assignmentcontrol information and thereby assigns not only assignment controlinformation (DCI 0/1A) indicating resource assignment information to beassigned to the anchor band (component band 1 in FIG. 6 ) configured forterminal 200 but also assignment control information (DCI 0/1A)indicating resource assignment information to be assigned to componentbands other than the anchor band only to CCEs within a UE-SS of theanchor band. Upon acquiring assignment control information of DCI 0/1Aaddressed to this terminal in the UE-SS of component band 1 (anchorband) shown in FIG. 6 , PDCCH reception section 207 of terminal 200identifies the component band indicated by a CI added to the assignmentcontrol information as a component band subject to resource assignment.

Although base station 100 transmits assignment control information ofDCI 0/1A for terminal-specific data assignment only in the anchor band(component band 1 in FIG. 6 ) configured for terminal 200, it ispossible to perform data assignment to all of the plurality of componentbands configured for terminal 200.

Thus, base station 100 can select a component band to transmit data suchas control information of an upper layer reported using DCI 0/1A (e.g.,control information reporting a change to an emergency-evacuation-liketransmission mode) for every transmission timing (e.g., in subframeunits), and therefore the degree of freedom of data assignment improves.For example, base station 100 follows an instantaneous variation in thechannel situation in subframe units, and can thereby transmit data suchas control information of an upper layer in a component band having agood channel situation. This makes it possible to realize datatransmission at a high coding rate, that is, high efficiency datatransmission with a small number of resources.

Furthermore, as in the case of Embodiment 1, assignment controlinformation of DCI 0/1A is assigned only to component band 1 which isthe anchor band shown in FIG. 6 . For this reason, terminal 200 maydesignate only component band 1 which is the anchor band of thisterminal as a blind decoding (monitoring) target for assignment controlinformation of DCI 0/1A. It is thereby possible to reduce the blinddecoding count of terminal 200 for which a plurality of component bandsare configured as in the case of Embodiment 1.

Thus, the present embodiment adds a CI to assignment control informationof DCI 0/1A assigned to a UE-SS, and can thereby reduce the blinddecoding count of the terminal even when a plurality of component bandsare configured for the terminal without increasing the CCE block rate asin the case of Embodiment 1 while improving the degree of freedom ofdata assignment.

Embodiment 3

In the present embodiment, a base station assigns assignment controlinformation of DCI 0/1A only to CCEs within respective C-SSs set in aplurality of component bands for a terminal for which a plurality ofcomponent bands are configured.

Hereinafter, the present embodiment will be described more specifically.Base station 100 (FIG. 1 ) and terminal 200 (FIG. 3 ) according to thepresent embodiment have configurations similar to those in Embodiment 1,but differ in the operation of assignment section 106 and PDCCHreception section 207. Furthermore, the operation when the number ofcomponent bands configured for the terminal is one is similar to that inEmbodiment 1 (FIG. 4 ), and therefore descriptions thereof will beomitted. That is, a case will be described below where a plurality ofcomponent bands are configured for the terminal.

Furthermore, in the following descriptions, component band configurationsection 101 (FIG. 1 ) of base station 100 configures a plurality ofdownlink component bands (component bands 1, 2, . . . ) for terminal 200(LTE-A terminal) as in the case of Embodiment 1 (FIG. 5 ) as shown inFIG. 7 . Furthermore, in FIG. 7 , base station 100 assumes that thenumber of CCEs making up a C-SS set in each component band is four andthe number of CCEs making up a UE-SS of each component band configuredfor terminal 200 is six as in the case of Embodiment 1 (FIG. 5 ).

For a terminal for which a plurality of component bands are configured,when assignment control information included in a PDCCH signal addressedto the terminal is a format common to all terminals (e.g., DCI 1C,0/1A), assignment section 106 of base station 100 (FIG. 1 ) according tothe present embodiment assigns the PDCCH signal only to CCEs withinC-SSs of respective C-SSs and UE-SSs set in a plurality of componentbands configured for the terminal. Furthermore, when assignment controlinformation included in the PDCCH signal is atransmission-mode-dependent DCI format (e.g., DCI 1, 2, 2A, 0A, 0B),assignment section 106 assigns the PDCCH signal to CCEs within a UE-SSset in the terminal in each component band as in the case ofEmbodiment 1. In this case, assignment section 106 assigns assignmentcontrol information to CCEs in a component band in which data subject toresource assignment indicated by the assignment control information istransmitted.

Specifically, assignment section 106 assigns a PDCCH signal includingassignment control information for shared channels (DCI 1C, 1A) and aPDCCH signal including assignment control information for dataassignment common to all terminals (DCI 0/1A) to any one of respectiveC-SSs set in a plurality of component bands (component bands 1, 2, . . .) shown in FIG. 7 . On the other hand, assignment section 106 assigns aPDCCH signal including transmission-mode-dependent assignment controlinformation (uplink (DCI 0A, 0B), downlink (DCI 1, 2, 2A)) set interminal 200 to CCEs in the respective UE-SSs of a plurality ofcomponent bands (component bands 1, 2, . . . ) shown in FIG. 7 .

That is, for a terminal for which a plurality of component bands areconfigured, assignment control information of DCI 0/1A is assigned onlyto CCEs within a C-SS of each component band and only assignment controlinformation in a transmission-mode-dependent DCI format is assigned to aUE-SS of each component band.

On the other hand, when a plurality of downlink component bands areindicated by band information input from configuration informationreception section 206, PDCCH reception section 207 of terminal 200 (FIG.3 ) performs blind decoding on a format common to all terminals for aC-SS of each component band configured for this terminal. Furthermore,PDCCH reception section 207 performs blind decoding on a DCI formatcorresponding to a transmission mode set in this terminal for a UE-SS ofeach component band configured for this terminal.

Specifically, PDCCH reception section 207 performs blind decoding on aPDCCH signal including assignment control information for sharedchannels (DCI 1C, 1A) and a PDCCH signal including assignment controlinformation for data assignment common to all terminals (DCI 0/1A) forrespective C-SSs of the plurality of component bands (component bands 1,2, . . . ) shown in FIG. 7 . Furthermore, PDCCH reception section 207performs blind decoding on a PDCCH signal includingtransmission-mode-dependent assignment control information (uplink (DCI0A, 0B), downlink (DCI 1, 2, 2A)) for respective UE-SSs of the pluralityof component bands (component bands 1, 2, . . . ) shown in FIG. 7 .

That is, when a plurality of component bands are configured for thisterminal, PDCCH reception section 207 performs blind decoding(monitoring) on a DCI format common to all terminals (DCI 1C, 0/1A) onlyfor a C-SS of a C-SS and UE-SS set in each component band. That is,PDCCH reception section 207 does not perform blind decoding (monitoring)on a PDCCH signal including assignment control information for dataassignment common to all terminals (DCI 0/1A) in a UE-SS of eachcomponent band. That is, PDCCH reception section 207 performs blinddecoding on two types of DCI format (DCI 1C and DCI 0/1A) in a C-SS ofeach component band shown in FIG. 7 and performs blind decoding on twotypes of DCI format (uplink transmission-mode-dependent DCI (DCI 0A, 0B)and downlink transmission-mode-dependent DCI (DCI 1, 2, 2A)) in a UE-SSof each component band.

Regarding a reduction of a blind decoding count, for example, a casewill be described where as shown, for example, in FIG. 2 , blinddecoding is performed six times on each DCI format for a C-SS and blinddecoding is performed 16 times on each DCI format for a UE-SS. In thiscase, PDCCH reception section 207 performs blind decoding a total of 44(=(6×2)+(16×2)) times per component band. That is, it is possible toreduce the blind decoding count by a blind decoding count (16 times)corresponding to one type of DCI format (DCI 0/1A) in a UE-SS of eachcomponent band shown in FIG. 7 .

For example, when five component bands are configured for terminal 200,when terminal 200 performs blind decoding on five types of DCI format inall component bands, blind decoding needs to be performed a total of 300times (60 times×5) as described above. By contrast, the presentembodiment requires blind decoding to be performed a total of 220 times(=44 times×5). That is, the present embodiment reduces blind decoding by80 times (=16 times×5).

Furthermore, base station 100 needs only to transmit assignment controlinformation of DCI 0/1A using any one C-SS of a plurality of componentbands configured for terminal 200. This allows base station 100 toselect a component band in which control information of an upper layerreported through DCI 0/1A (e.g., control information reporting a changeto an emergency-evacuation-like transmission mode) is transmitted fromamong a plurality of component bands, and it is thereby possible toimprove the degree of freedom of data assignment as in the case ofEmbodiment 2. The above-described upper-layer control information may betransmitted in any one of a plurality of less frequently used componentbands configured for terminal 200. Therefore, even when base station 100transmits assignment control information of DCI 0/1A using only a C-SSof each component band, the possibility of the CCE block rate increasingdue to contention of CCEs with other terminals is low.

Thus, according to the present embodiment, when a plurality of componentbands are configured for the terminal, the base station assignsassignment control information for data assignment common to a pluralityof terminals only to a C-SS of each component band. As described above,the blind decoding count in the terminal can be reduced by an amountcorresponding to the blind decoding on assignment control informationfor data assignment common to a plurality of terminals in a UE-SS thatbecomes unnecessary. Furthermore, since the base station can select acomponent band to assign assignment control information for dataassignment common to a plurality of terminals from among a plurality ofcomponent bands configured for the terminal, the possibility of the CCEblock rate increasing due to contention of CCEs with other terminalsdecreases. Thus, the present embodiment can reduce the blind decodingcount of the terminal even when a plurality of component bands areconfigured for the terminal without increasing the CCE block rate as inthe case of Embodiment 1.

Embodiment 4

The present embodiment differs from Embodiment 2 in that, when aplurality of component bands are configured for a terminal, all searchspaces corresponding to the plurality of component bands are set in ananchor band configured for the terminal.

Hereinafter, the present embodiment will be described more specifically.Base station 100 (FIG. 1 ) and terminal 200 (FIG. 3 ) according to thepresent embodiment have configurations similar to those of Embodiment 1,but the operation of component band configuration section 101, searchspace setting section 103, assignment section 106, configurationinformation reception section 206 and PDCCH reception section 207differs.

In addition to processing similar to that in Embodiment 1, componentband configuration section 101 of base station 100 (FIG. 1 ) accordingto the present embodiment configures one component band (hereinafteralso referred to as “PDCCH transmission component band) used fortransmission of a PDCCH signal for each terminal. For example, componentband configuration section 101 configures an anchor band of eachterminal as a PDCCH transmission component band.

In a terminal for which a plurality of component bands are configured,search space setting section 103 sets the same number of UE-SSs as theplurality of component bands configured for the terminal in the PDCCHtransmission component band configured by component band configurationsection 101. That is, search space setting section 103 sets searchspaces corresponding to the plurality of component bands configured forthe terminal in the PDCCH transmission component band. That is, searchspace setting section 103 sets all UE-SSs corresponding to the pluralityof component bands configured for the terminal in a specific componentband (anchor band, that is, PDCCH transmission component band). Forexample, search space setting section 103 sets L CCEs starting from aCCE number calculated using a terminal ID of the terminal and a hashfunction that performs randomization in a UE-SS of a first componentband, and sets L CCEs starting from a CCE next to the CCE (last CCE) setin the UE-SS of the first component band in a UE-SS of a secondcomponent band.

When assignment control information included in a PDCCH signal addressedto a terminal for which a plurality of component bands are configured isa DCI format common to all terminals (DCI 0/1A) and a CI is addedthereto, assignment section 106 assigns the PDCCH signal to CCEs withina UE-SS corresponding to an anchor band configured for the terminalamong UE-SSs corresponding to a plurality of component bands set in aPDCCH transmission component band set by search space setting section103. On the other hand, when assignment control information included inthe PDCCH signal is a DCI format common to all terminals (DCI 0/1A) andno CI is added thereto, assignment section 106 assigns the PDCCH signalto CCEs within a C-SS. Furthermore, when the assignment controlinformation included in the PDCCH signal is atransmission-mode-dependent DCI format (DCI 0/1A), assignment section106 assigns the PDCCH signal to a UE-SS corresponding to a componentband in which data subject to resource assignment indicated by theassignment control information is transmitted among a plurality ofUE-SSs set in the PDCCH transmission component band. Thus, assignmentsection 106 assigns all PDCCH signals addressed to a terminal for whicha plurality of component bands are configured to a PDCCH transmissioncomponent band.

On the other hand, configuration information reception section 206 ofterminal 200 (FIG. 3 ) reads information indicating a PDCCH transmissioncomponent band configured for this terminal from a control signal inputfrom separation section 205 and outputs the information to PDCCHreception section 207.

PDCCH reception section 207 calculates a UE-SS corresponding to eachcomponent band configured for this terminal in the same way as searchspace setting section 103 in a PDCCH transmission component bandindicated by the information input from configuration informationreception section 206. PDCCH reception section 207 performs blinddecoding (monitoring) on a UE-SS corresponding to each calculatedcomponent band focused on a DCI format corresponding to a transmissionmode set in this terminal. Furthermore, PDCCH reception section 207performs blind decoding only on a UE-SS corresponding to an anchor band(specific component band) among UE-SSs corresponding to a plurality ofcomponent bands set in the PDCCH transmission component band focused ona DCI format common to all terminals (DCI 0/1A (with a CI)). That is,PDCCH reception section 207 performs blind decoding (monitoring) only onCCEs within a UE-SS corresponding to an anchor band (specific componentband) among UE-SSs corresponding to a plurality of component bands setin the anchor band (specific component band), and thereby acquiresassignment control information with a CI. Here, when assignment controlinformation with a CI is acquired as a result of performing blinddecoding (monitoring) on the UE-SS corresponding to the anchor band,terminal 200 assigns data (e.g., control information of an upper layer)based on the resource assignment information indicated by the assignmentcontrol information in the component band indicated by the CI.

Next, details of PDCCH signal assignment processing in assignmentsection 106 of base station 100 and blind decoding (monitoring)processing in PDCCH reception section 207 of terminal 200 will bedescribed.

In the following description, as shown in FIG. 8 , component bandconfiguration section 101 (FIG. 1 ) of base station 100 configures aplurality of downlink component bands (component bands 1, 2, . . . ) forterminal 200 (LTE-A terminal) as in the case of Embodiment 1 (FIG. 5 ).Furthermore, component band configuration section 101 configurescomponent band 1 as an anchor band of terminal 200 as shown in FIG. 8 .Furthermore, component band configuration section 101 configurescomponent band 1 (anchor band) shown in FIG. 8 as a PDCCH transmissioncomponent band. The PDCCH transmission component band is separatelyreported to terminal 200 as upper-layer control information (RRC controlinformation). As the PDCCH transmission component band, for example, acomponent band having a good channel situation (component band having ahigher SIR, component band having higher receiving power, component bandhaving smaller channel attenuation (path loss)) or a component band withless interference from other cells is configured.

Furthermore, in FIG. 8 , base station 100 assumes that the number ofCCEs making up a C-SS set in each component band is four and the numberof CCEs making up a UE-SS in each component band configured for terminal200 is six as in the case of Embodiment 1 (FIG. 5 ).

For terminal 200 for which a plurality of component bands areconfigured, search space setting section 103 of base station 100 setsall UE-SSs corresponding to the plurality of component bands configuredfor terminal 200 in component band 1 (anchor band) which is a PDCCHtransmission component band.

For example, assuming that a CCE number calculated from the terminal IDof terminal 200 and a hash function is m and the number of CCEs makingup a search space is L, search space setting section 103 sets CCEs ofCCE numbers m to (m+(L−1)) in UE-SSs corresponding to component band 1(anchor band) as shown in FIG. 8 . Similarly, search space settingsection 103 sets CCEs of CCE numbers (m+L) to (m+(2 L−1)) in UE-SSscorresponding to component band 2 as shown in FIG. 8 . That is, searchspace setting section 103 sets CCE numbers (m+(k−1)L) to (m+(kL−1)) insearch spaces corresponding to component band k. When a CCE numberreaches the last CCE number, search space setting section 103 may resetthe CCE number to 0, that is, adopt mod NCCE for CCE numbers used forsetting search spaces. Here, “mod” is a modulo operation and “NCCE” isthe number of CCEs making up a PDCCH of a PDCCH transmission componentband.

In component band 1 (PDCCH transmission component band) shown in FIG. 8, assignment section 106 assigns a PDCCH signal whose assignment controlinformation has no CI among PDCCH signals including assignment controlinformation for data assignment common to all terminals (DCI 0/1A) toCCEs within a C-SS and assigns a PDCCH signal whose assignment controlinformation has a CI to CCEs within a UE-SS corresponding to componentband 1 which is an anchor band.

Furthermore, in component band 1 (PDCCH transmission component band)shown in FIG. 8 , assignment section 106 assignstransmission-mode-dependent assignment control information (uplink (DCI0A, 0B), downlink (DCI 1, 2, 2A)) set in terminal 200 to CCEs in a UE-SScorresponding to a component band in which data subject to resourceassignment indicated by the assignment control information istransmitted. For example, when the component band in which data subjectto resource assignment indicated by the transmission-mode-dependentassignment control information is transmitted is assumed to be componentband 2 shown in FIG. 8 , assignment section 106 assigns a PDCCH signalincluding the assignment control information to CCEs in a UE-SScorresponding to component band 2 in component band 1 shown in FIG. 8 .

On the other hand, PDCCH reception section 207 of terminal 200 performsblind decoding on a PDCCH signal including assignment controlinformation for shared channels (DCI 1C, 1A) and a PDCCH signalincluding assignment control information for data assignment common toall terminals (DCI 0/1A (without a CI)) for the C-SS of component band 1(anchor band) shown in FIG. 8 . Furthermore, PDCCH reception section 207performs blind decoding on a PDCCH signal includingtransmission-mode-dependent assignment control information (uplink (DCI0A, 0B), downlink (DCI 1, 2, 2A)) for UE-SSs corresponding to componentbands (component bands 1, 2, . . . ) configured for this terminal incomponent band 1 shown in FIG. 8 .

Furthermore, PDCCH reception section 207 performs blind decoding on aPDCCH signal including assignment control information for dataassignment common to all terminals (DCI 0/1A (with a CI)) for a UE-SScorresponding to component band 1 which is an anchor band among UE-SSscorresponding to a plurality of component bands set in component band 1(PDCCH transmission component band) shown in FIG. 8 . At this time,PDCCH reception section 207 performs blind decoding focused on the sizeof assignment control information with a CI.

Thus, upon acquiring assignment control information of DCI 0/1Aaddressed to this terminal in a UE-SS corresponding to component band 1set in component band 1 shown in FIG. 8 , terminal 200 identifies acomponent band indicated by the CI added to the assignment controlinformation as a component band subject to resource assignment. That is,although base station 100 transmits assignment control information ofDCI 0/1A for terminal-specific data assignment using only an anchor band(PDCCH transmission component band) configured for terminal 200 as inthe case of Embodiment 2, base station 100 can assign data to aplurality of component bands.

Thus, as in the case of Embodiment 2, base station 100 can select acomponent band to transmit data such as control information of an upperlayer to be reported using DCI 0/1A (e.g., control information reportinga change to an emergency-evacuation-like transmission mode) for eachtransmission timing (e.g., in subframe units), and thereby improves thedegree of freedom of data assignment. For example, base station 100follows an instantaneous variation in a channel situation in subframeunits, can thereby transmit data such as control information of an upperlayer in a component band having a good channel situation, and canthereby realize data transmission at a high coding rate, that is, highefficiency data transmission with a small number of resources.

Furthermore, assignment control information of DCI 0/1A is assigned onlyto component band 1 (PDCCH transmission component band) shown in FIG. 8. Therefore, for assignment information of DCI 0/1A, terminal 200 needsonly to designate only component band 1 which is a PDCCH transmissioncomponent band as a blind decoding (monitoring) target. Thus, as in thecase of Embodiment 1, it is possible to reduce the blind decoding countof terminal 200 for which a plurality of component bands are configured.

Furthermore, base station 100 can set a component band having a goodchannel situation as a PDCCH transmission component band for eachterminal. Thus, the base station can transmit a PDCCH signal to eachterminal in a component band having a good channel situation, and canthereby improve an error rate characteristic of the PDCCH signal andrealize signal transmission at a high coding rate, that is, highefficiency signal transmission with a small number of resources (numberof CCEs).

Thus, even when a plurality of component bands are configured for aterminal, the present embodiment can reduce the blind decoding count ofthe terminal without increasing a CCE block rate as in the case ofEmbodiment 1. Furthermore, the present embodiment adds a CI toassignment control information of DCI 0/1A assigned to a UE-SS, and canthereby improve the degree of freedom of data assignment as in the caseof Embodiment 2. Furthermore, the present embodiment sets all searchspaces to transmit PDCCH signals in a plurality of component bands inone component band having a good channel situation, and can therebyimprove error rate characteristics of PDCCH signals.

In the present embodiment, a PDCCH transmission component band may alsobe set in common to all terminals for each cell. For example, whenfrequency bands of a plurality of component bands are different (e.g.,component band 1 is an 800 MHz band and component band 2 is 3.4 MHzband), the base station may set the component band having a lowerfrequency (component band 1 of an 800 MHz band) as the PDCCHtransmission component band. Here, the lower the frequency of thefrequency band, the smaller is the channel attenuation (path loss).Therefore, by setting a component band having a lower frequency as thePDCCH transmission component band, it is possible to realize robusterand high efficiency signal transmission.

Furthermore, the present embodiment may also apply a configuration inwhich no CI is added to assignment control information of DCI 0/1A. Inthe present embodiment, assignment control information of DCI 0/1A isassigned to a UE-SS corresponding to a PDCCH transmission component band(component band 1 which is an anchor band in FIG. 8 ). Therefore, by thebase station selecting a component band having a good channel situationas the PDCCH transmission component band beforehand, it is possible totransmit assignment control information of DCI 0/1A and data subject toresource assignment indicated by the assignment control information in aPDCCH transmission component band which is a component band having agood channel situation without adding a CI for indicating a componentband having a good channel situation.

Furthermore, a case has been described in the present embodiment whereassignment control information of DCI 0/1A is assigned to a UE-SScorresponding to an anchor band. However, in the present embodiment, theUE-SS to which assignment control information of DCI 0/1A is assigned isnot limited a UE-SS corresponding to an anchor band, but assignmentcontrol information may be assigned to a UE-SS corresponding to anycomponent band. No matter to which component band a UE-SS corresponds towhich assignment control information of DCI 0/1A is assigned, theterminal needs only to perform blind decoding on DCI 0/1A using only aUE-SS corresponding to one component band of UE-SSs corresponding to aplurality of component bands, and therefore the blind decoding count ofthe terminal can be reduced as in the case of the above embodiments.

A case has been described in the present embodiment where the number ofPDCCH transmission component bands is one, but the number of PDCCHtransmission component bands may also be plural in the presentinvention.

Furthermore, the PDCCH transmission component band used in the presentembodiment may also be referred to as “UE PDCCH component carrier set.”

This concludes a description of embodiments of the present invention.

Band aggregation may also be referred to as “carrier aggregation.” Also,band aggregation is not limited to a case in which continuous frequencybands are aggregated, and non-continuous frequency bands may also beaggregated.

In the present invention, a C-RNTI (Cell-Radio Network TemporaryIdentifier) may be used as a terminal ID.

In the above embodiments, a case has been described in which a componentband is defined as a band that has a maximum width of 20 MHz, and is abasic communication band unit. However, a component band may also bedefined as follows. For example, a downlink component band may bedefined as a band delimited by downlink frequency band information in aBCH (Broadcast Channel) notified from a base station, or a band definedby a distribution width when a PDCCH is subjected to distributedplacement in a frequency band. Also, an uplink component band may alsobe defined as a band delimited by uplink frequency band information in aBCH notified from a base station, or a basic communication band unit of20 MHz or less that includes a PUSCH near the center and a PUCCH at bothends. A component band may also be referred to as a component carrier inLTE.

Furthermore, as for a component band configured as an anchor band, thepresent invention may configure a component band configured beforehandin the system (e.g., component band that transmits SCH or P-BCH) or acomponent band common to terminals for each cell or different componentbands for each terminal.

Furthermore, an anchor band may also be referred to as “anchor carrier,”“master band (master carrier)” or “primary band (primary carrier).”

Furthermore, in the above embodiments, the expression “DCI format commonto all terminals” may also be read as “DCI format independent oftransmission mode.”

A case has been described in the above embodiments where DCI 0/1A isused as a “DCI format common to all terminals.” However, in the presentinvention, the “DCI format common to all terminals” is not limited toDCI 0/1A, but may be any DCI format used independently of thetransmission mode.

Furthermore, a case has been described in the above embodiments whereDCI 0A, 0B, 1, 2, 2A is used as the transmission-mode-dependent DCI.However, the present invention may also use any format other than DCI0A, 0B, 1, 2, 2A as the transmission-mode-dependent DCI.

Furthermore, the present invention may also use DCI 0 (continuous bandassignment transmissions on an uplink) and DCI 1A (continuous bandassignment transmissions on a downlink) as thetransmission-mode-dependent DCI. In this case, the DCI format common toall terminals (DCI 0/1A) and transmission-mode-dependent DCI format areidentical. For this reason, in a UE-SS set in a terminal, the terminalmay perform blind decoding focused on one type of DCI format on anuplink (DCI 0, 0A, 0B) and downlink (1, 1A, 2, 2A). When thetransmission modes of the uplink and downlink are both continuous bandassignment (in the case of DCI 0/1A), the terminal may perform blinddecoding focused on one type of DCI format combining the uplink anddownlink. By this means, DCI 0/1A may be used as atransmission-mode-dependent DCI having a wider search space. In thisway, the base station can also assign assignment control information ofDCI 0/1A to CCEs in a wider search space to also a terminal having apoor channel situation to which only assignment control information ofDCI 0/1A can be assigned, and can thereby prevent the CCE block ratefrom increasing.

Furthermore, a component band configured for each terminal may beconfigured for an uplink and downlink independently. Furthermore, acomponent band configured for an uplink may also be referred to as “UEUL Component Carrier Set” and a component band configured for a downlinkmay also be referred to as “UE DL Component Carrier Set.”

A case has been described in above Embodiments 2 and 4 where a CI bit isadded when performing data assignment in different component bands.However, the present invention is not limited to a case where a CI bitis added, but different component bands may be indicated using othermethods. For example, the CRC portion may be masked with a codecorresponding to a component band subject to assignment or differentsearch spaces may be set for each component band subject to assignmentto thereby distinguish between component bands subject to assignment.

A CCE described in the above embodiments is a logical resource, and whenplaced on an actual physical time/frequency resource, CCE distributionis performed across the entire band within a component band. Also, aslong as CCEs functioning as logical resources are divided on anindividual component band basis, CCE placement on an actual physicaltime/frequency resource may be distributed across the entire system band(that is, all component bands).

A mobile station may also be referred to as UE, and a base station asNode B or BS (Base Station). A terminal ID may also be referred to asUE-ID.

Also, although cases have been described with the above embodiment asexamples where the present invention is configured by hardware, thepresent invention can also be realized by software.

Each function block employed in the description of each of theaforementioned embodiments may typically be implemented as an LSIconstituted by an integrated circuit. These may be individual chips orpartially or totally contained on a single chip. “LSI” is adopted herebut this may also be referred to as “IC,” “system LSI,” “super LSI,” or“ultra LSI” depending on differing extents of integration.

Further, the method of circuit integration is not limited to LSI's, andimplementation using dedicated circuitry or general purpose processorsis also possible. After LSI manufacture, utilization of a programmableFPGA (Field Programmable Gate Array) or a reconfigurable processor whereconnections and settings of circuit cells within an LSI can bereconfigured is also possible.

Further, if integrated circuit technology comes out to replace LSI's asa result of the advancement of semiconductor technology or a derivativeother technology, it is naturally also possible to carry out functionblock integration using this technology. Application of biotechnology isalso possible.

The disclosure of Japanese Patent Application No. 2009-188721, filed onAug. 17, 2009, including the specification, drawings and abstract isincorporated herein by reference in its entirety.

INDUSTRIAL APPLICABILITY

The present invention is suitable for use in a mobile communicationsystem or the like.

REFERENCE SIGNS LIST

-   -   100 base station    -   101 component band configuration section    -   102 control section    -   103 search space setting section    -   104 PDCCH generation section    -   105, 107, 108 encoding/modulation section    -   106 assignment section    -   109 multiplexing section    -   110, 213 IFFT section    -   111, 214 CP addition section    -   112, 215 radio transmission section    -   113, 201 antenna    -   114, 202 radio reception section    -   115, 203 CP removal section    -   116, 204 FFT section    -   117 extraction section    -   118 IDFT section    -   119 data reception section    -   120 ACK/NACK reception section    -   200 terminal    -   205 separation section    -   206 configuration information reception section    -   207 PDCCH reception section    -   208 PDSCH reception section    -   209, 210 modulation section    -   211 DFT section    -   212 mapping section

1. A communication apparatus comprising: circuitry, which, in operation,configures at least one of a common search space that is common to aplurality of terminals and a UE specific search space that is specificto each of the plurality of terminals; and a transmitter, which, inoperation, controls transmission of control information includingresource assignment information in at least one of the common searchspace and the UE specific search space, wherein the control informationincluding a carrier indicator that indicates one of a plurality ofcomponent carriers is transmitted in the UE specific search space, thecontrol information including no carrier indicator is transmitted onlyin the common search space, and UE specific search spaces, whichrespectively correspond to the plurality of component carriers, areconfigured in a primary component carrier of the plurality of componentcarriers.
 2. The communication apparatus according to claim 1, whereinthe carrier indicator indicates the component carrier, in which aresource is allocated by the resource assignment information.
 3. Thecommunication apparatus according to claim 1, wherein the controlinformation is transmitted in a primary component carrier of theplurality of component carriers.
 4. A communication method comprising:configuring at least one of a common search space that is common to aplurality of terminals and a UE specific search space that is specificto each of the plurality of terminals; and controlling transmission ofcontrol information including resource assignment information in atleast one of the common search space and the UE specific search space,wherein the control information including a carrier indicator thatindicates one of a plurality of component carriers is transmitted in theUE specific search space, the control information including no carrierindicator is transmitted only in the common search space, and UEspecific search spaces, which respectively correspond to the pluralityof component carriers, are configured in a primary component carrier ofthe plurality of component carriers.
 5. The communication methodaccording to claim 4, wherein the carrier indicator indicates thecomponent carrier, in which a resource is allocated by the resourceassignment information.
 6. The communication method according to claim4, wherein the control information is transmitted in a primary componentcarrier of the plurality of component carriers.